package com.zhang.factory.example.utils;

import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.List;

/**
 * @author ElloeStudy(Sifa Zhang)
 * @create 2022-02-28 20:45
 * To: 真常应物，真常得性，常清常静，常清静矣
 */
public class ClassUtils {
    // 给一个接口，返回这个接口的所有实现类
    public static List<Class> getAllClassByInterface(Class c) {
        List<Class> returnClassList = new ArrayList<Class>();  // 返回的结果

        // 如果不是一个接口，则不做处理
        if (c.isInterface()){
            String packageName = c.getPackage().getName();  // 获得当前的包名

            try {
                List<Class> allClass = getClasses(packageName);// 获得当前包下及子包下的所有类
                // 判断是否是同一个接口
                for (int i = 0; i < allClass.size(); i++) {
                    if (c.isAssignableFrom(allClass.get(i))){  // 判断是不是一个接口
                        if (!c.equals(allClass.get(i))){  //本身不加进去
                            returnClassList.add(allClass.get(i));
                        }
                    }
                }
            } catch (IOException e) {
                e.printStackTrace();
            } catch (ClassNotFoundException e) {
                e.printStackTrace();
            }
        }
        return  returnClassList;
    }

    // 从一个包里面查找所有的类，在jar包不能查找
    private  static List<Class> getClasses(String packageName) throws IOException, ClassNotFoundException {
        ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
        String path = packageName.replace('.', '/');
        Enumeration<URL> resources = classLoader.getResources(path);
        List<File> dirs = new ArrayList<File>();
        while (resources.hasMoreElements()){
            URL resource = resources.nextElement();
            dirs.add(new File(resource.getFile()));
        }
        ArrayList<Class> classes = new ArrayList<Class>();
        for (File directory:dirs){
            classes.addAll(findClasses(directory,packageName));
        }
        return classes;
    }

    private static List<Class> findClasses(File directory,String packageName) throws ClassNotFoundException {
        List<Class> classes = new ArrayList<Class>();
        if (!directory.exists()){
            return classes;
        }
        File[] files = directory.listFiles();
        for (File file : files) {
            if (file.isDirectory()){
                assert !file.getName().contains(".");
                classes.addAll(findClasses(file,packageName + "." + file.getName()));
            }else if (file.getName().endsWith(".class")){
                classes.add(Class.forName(packageName + '.' + file.getName().substring(0,file.getName().length()-6)));
            }
        }
        return classes;
    }
}
